Layers Of The Earth: What Lies Beneath Earth's Crust Layers Of The Earth: What Lies Beneath Earth's Crust {{article.article.images.featured.caption}} Opinions expressed by Forbes Contributors are their own. Full Bio The author is a Forbes contributor. The opinions expressed are those of the writer. Loading ... This story appears in the {{article.article.magazine.pretty_date}} issue of {{article.article.magazine.pubName}}. Subscribe The layers of Earth (Credit: The layers of Earth provide geologists and geophysicists clues to how Earth formed, the layers that make up other planetary bodies, the source of Earth's resources, and much more. Modern advances have allowed scientists to study what lies beneath our feet in more detail than ever before and yet there still remains significant gaps in our understanding. I hope this guide will walk you through the layers of the Earth, provide a general sense of our understanding and our current gaps. Keep in mind that this is an area of ongoing research and is likely to become more refined in the coming years and decades. During my second year at Edinburgh [1826-27] I attended Jameson's lectures on Geology and Zoology, but they were incredible dull.

The sole effect they produced on me was the determination never as long as I lived to read a book on Geology. - Charles Darwin The Layers Of Earth The Earth has layers not unlike an onion and can be dissected to understand the physical and chemical properties of each layer and its influence on the rest of the Earth. Generally speaking, Earth has 4 layers: the outer crust that we live on, the plastic-like mantle, the liquid outer core, and the solid inner core. When differentiating the layers, geologists lump subdivisions into two categories, either rheologically or chemically. Rheological differentiation speaks to the liquid state of rocks under tremendous pressure and temperature. For instance, rock will respond very differently to strain under normal atmospheric temperatures and pressures as compared to fewer than thousands of kilometers of rock. If we subdivide the Earth based on rheology, we see the lithosphere, asthenosphere, mesosphere, outer core, and inner core. However, if we differentiate the layers based on chemical variations, we lump the layers into crust, mantle, outer core, and inner core. To understand the difference in various portions of the mantle or outer versus inner core you must understand phase diagrams, which I will speak on below.

A cartoon block of the layers of earth (Credit: USGS) Earth's Crust The crust is what you and I live on and is by far the thinnest of the layers of earth. The thickness varies depending on where you are on earth, with oceanic crust being 5-10 km and continental mountain ranges being up to 30-45 km thick. Thin oceanic crust is denser than the thicker continental crust and therefore 'floats' lower in the mantle as compared to continental crust. You will find some of the thinnest oceanic crust along mid ocean ridges where new crust is actively being formed. In comparison, when two continents collide as in the case of the India Plate and Eurasia Plate, you get some of the thickest sections of crust as it is crumpled together. The temperatures within Earth's crust will vary from air temperatures at the surface to approximately 870 degrees Celsius in deeper sections. At this temperature, you begin to melt rock and form the below-lying mantle. Geologists subdivide Earth's crust into different plates that move about in relation to one another. Given that Earth's surface is mostly constant in area, you cannot make crust without destroying a comparable amount of crust.

With convection of the underlying mantle, we see insertion of mantle magma along mid ocean ridges, constantly forming new oceanic crust. However, to make room for this, oceanic crust must subduct (sink below) continental crust. Geologists have studied extensively the history of this plate movement, but we are sorely lacking in determining why and how these plates move the way they do. Plate tectonic map of the Earth (Credit: USGS) Earth's crust "floats" on top of the soft plastic-like mantle below. In some instances mantle clearly drives changes in the crust, as in the Hawaiian Islands. However, there is ongoing debate whether oceanic crust subduction and mid ocean ridge spreading is driven by a push or pull mechanism. In very broad terms, oceanic crust is made up of basalt and continental crust is made up of rocks similar to granite. Below the crust is a solid relatively cooler portion of the upper mantle that is combined with the crust to make the lithosphere layer. The lithosphere is physically distinct from the below-lying layers due to its cool temperatures and typically extends 70-100 km in depth.

Below the lithosphere is the asthenosphere layer, a much hotter and malleable portion of the upper mantle. The asthenosphere begins at the bottom of the lithosphere and extends approximately 700 km into the Earth. The asthenosphere acts as the lubricating layer below the lithosphere that allows the lithosphere to move over the Earth's surface. Earth's Mantle The mantle is the layer of the earth that lies below the crust and is by far the largest layer making up 84% of Earth's volume. The mantle starts at the Mohorovicic Discontinuity , also known as the Moho. The Moho is defined as the density contrast from less dense crust to denser mantle and where seismic wave velocities increase. The mantle acts similar to plastic and at very high temperatures and pressures the rock is deformable at geologic timescales. This deformation causes a convection like process in the mantle where you have larige-scale upwelling and downwelling zones. The mantle extends down to 2,890 km into the Earth's surface Temperatures that range from 500 to 900 degrees Celsius in the upper portion to over 4,000 degrees Celsius near the core boundary.

Earth's mantle is believed to be composed of bulk mineralogy similar to peridotite . Gem quality peridotite is called peridot, so next time you're in a jewelry shop take a look at the peridot and you'll be looking at something similar to 84% of Earth! The video above provides a glimpse into the global circulation of mantle magma around the Earth. Of course, this is greatly simplified but provides a schematic of the process creating mid ocean ridges, volcanoes, and mountains. Earth's Outer Core The outer core is the liquid largely iron layer of the earth that lies below the mantle. Geologists have confirmed that the outer core is liquid due to seismic surveys of Earth's interior. The outer core is 2,300 km thick and goes down to approximately 3,400 km into the earth. No one has ever seen the outer core but based on a number of indicators, geologists believe the outer core is 80% iron, some nickel and a number of different lighter elements. When Earth was just beginning to cool billions of years ago, heavier elements sunk down into the center of the Earth, while less dense elements rose to the surface.

Therefore, we see a general increase in density, as you get closer to the center of the Earth. The outer core is hot enough to be melted but not under quite enough pressure to make the iron solid again, as seen in the inner core. The temperature of the outer core ranges from about 4,030 to 5,730 degrees Celsius. Amazingly, the outer core is fluid enough and low enough in viscosity that it may spins faster than the entire Earth. This differential velocity of spinning, along with convection and turbulent flow of the iron outer core, creates Earth's magnetic field. A schematic of Earth's magnetic field (Credit: NASA) Earth's Inner Core The inner core is the centermost layer of Earth and is in many ways similar to the outer core. It is also primarily iron and nickel and has a radius of about 1,220 km. The differentiation between the outer core and inner core is density driven. The pressures become high enough that despite very high temperatures, the inner core is solid. It is also enriched in unusual heavy elements including gold, silver, platinum, palladium, and tungsten.

Temperatures reach up to 5,400 degrees Celsius and pressures up to 360 gigapascal. The inner core is about 70% of the Moon's radius and is approximately the same temperature as the surface of the Sun! Now, let's answer some commonly asked questions in case you're looking for quick answers. Frequently Asked Questions About Earth's Layers What is the outer layer of the Earth? The outer layer of the Earth is the crust, a hard thin layer that is composed of continental and oceanic crust. What are the different parts of the Earth? The different parts of the Earth are the crust, mantle, outer core, and inner core. How many layers are there in the Earth? There are 4 layers in Earth generally speaking. However, it depends how you measure each layer, based on physical or chemical properties. What is the depth of the inner core of the Earth? The inner core of the earth starts at 5,150 km from the Earth's surface and extends to the center of the Earth. What materials make up the inner core? The inner core is made up of primarily iron at 80% and nickel, along with trace amounts of heavy metals.

How deep is the Earth's crust? Earth's crust ranges from 5 to 60 kilometers depending on oceanic versus continental crust What are the two types of Earth's crust? The two types of crust are the dense and thin oceanic crust and less dense and thicker continental crust. I hope you enjoyed this guide to the layers of the Earth and it sparked a newfound interest in what lies beneath our feet! Trevor Nace is a geologist, Forbes contributor, and adventurer. Follow him on Twitter @trevornace crust - National Geographic Society crust Earth's crust is made of young oceanic material and older, thicker continental material. Map by USGS Silicates, Silicates Everywhere Silicate minerals, mostly feldspars and quartz, are the most abundant minerals in Earth’s rocky crust. Old Crust The oldest rocks yet identified on Earth were discovered in the Jack Hills of Western Australia, part of the Yilgarn Craton, a shield formation. The Jack Hills zircons are about 4.4 billion years old.

(The Earth itself is about 4.6 billion years old!) Mining Temperature The TauTona and Mponeng gold mines of South Africa are the deepest in the world, descending about 4 kilometers (2.5 miles) below the surface of the Earth. Although those are deep mines, they are shallow crust. Still, temperatures at the bottom of the mines can climb to 55° Celsius (131° Fahrenheit). A sophisticated air conditioning system lowers the temperature to allow miners to work. “ Crust ” describes the outermost shell of a terrestrial planet . Our planet ’s thin, 40-kilometer (25-mile) deep crust—just 1% of Earth’s mass—contains all known life in the universe . Earth has three layers: the crust, the mantle, and the core. The crust is made of solid rock s and mineral s. Beneath the crust is the mantle , which is also mostly solid rocks and minerals, but punctuated by malleable areas of semi-solid magma . At the center of the Earth is a hot, dense metal core . Earth’s layers constantly interact with each other, and the crust and upper portion of the mantle are part of a single geologic unit called the lithosphere .

The lithosphere’s depth varies, and the Mohorovicic discontinuity (the Moho)—the boundary between the mantle and crust—does not exist at a uniform depth. Isostasy describes the physical, chemical, and mechanical differences between the mantle and crust that allow the crust to “float” on the more malleable mantle. Not all regions of Earth are balanced in isostatic equilibrium. Isostatic equilibrium depends on the density and thickness of the crust, and the dynamic forces at work in the mantle. Just as the depth of the crust varies, so does its temperature . The upper crust withstands the ambient temperature of the atmosphere or ocean—hot in arid desert s and freezing in ocean trench es. Near the Moho, the temperature of the crust ranges from 200° Celsius (392° Fahrenheit) to 400° Celsius (752° Fahrenheit). Crafting the Crust Billions of years ago, the planetary blob that would become the Earth started out as a hot, viscous ball of rock. The heaviest material, mostly iron and nickel, sank to the center of the new planet and became its core. The molten material that surrounded the core was the early mantle.

Over millions of years, the mantle cooled. Water trapped inside minerals erupted with lava, a process called “ outgas sing.” As more water was outgassed, the mantle solidified. Materials that initially stayed in their liquid phase during this process, called “ incompatible element s,” ultimately became Earth’s brittle crust. From mud and clay to diamonds and coal, Earth’s crust is composed of igneous, metamorphic, and sedimentary rocks. The most abundant rocks in the crust are igneous, which are formed by the cooling of magma. Earth’s crust is rich in igneous rock s such as granite and basalt . Metamorphic rock s have undergone drastic changes due to heat and pressure. Slate and marble are familiar metamorphic rocks. Sedimentary rock s are formed by the accumulation of material at Earth’s surface. Sandstone and shale are sedimentary rocks. Dynamic geologic forces created Earth’s crust, and the crust continues to be shaped by the planet’s movement and energy. Today, tectonic activity is responsible for the formation (and destruction) of crustal materials. Earth’s crust is divided into two types: oceanic crust and continental crust. The transition zone between these two types of crust is sometimes called the Conrad discontinuity .

Silicate s (mostly compounds made of silicon and oxygen) are the most abundant rocks and minerals in both oceanic and continental crust. Oceanic Crust Oceanic crust , extending 5-10 kilometers (3-6 kilometers) beneath the ocean floor, is mostly composed of different types of basalts. Geologists often refer to the rocks of the oceanic crust as “sima.” Sima stands for silicate and magnesium, the most abundant minerals in oceanic crust. (Basalts are a sima rocks.) Oceanic crust is dense, almost 3 grams per cubic centimeter (1.7 ounces per cubic inch). Oceanic crust is constantly formed at mid-ocean ridge s, where tectonic plate s are tearing apart from each other. As magma that wells up from these rifts in Earth’s surface cools, it becomes young oceanic crust. The age and density of oceanic crust increases with distance from mid-ocean ridges. Just as oceanic crust is formed at mid-ocean ridges, it is destroyed in subduction zone s.

Subduction is the important geologic process in which a tectonic plate made of dense lithospheric material melts or falls below a plate made of less-dense lithosphere at a convergent plate boundary . At convergent plate boundaries between continental and oceanic lithosphere, the dense oceanic lithosphere (including the crust) always subducts beneath the continental. In the northwestern United States, for example, the oceanic Juan de Fuca plate subducts beneath the continental North American plate. At convergent boundaries between two plates carrying oceanic lithosphere, the denser (usually the larger and deeper ocean basin ) subducts. In the Japan Trench, the dense Pacific plate subducts beneath the less-dense Okhotsk plate. As the lithosphere subducts, it sinks into the mantle, becoming more plastic and ductile . Through mantle convection , the rich minerals of the mantle may be ultimately “recycled” as they surface as crust-making lava at mid-ocean ridges and volcano es. Largely due to subduction, oceanic crust is much, much younger than continental crust. The oldest existing oceanic crust is in the Ionian Sea, part of the eastern Mediterranean basin.

The seafloor of the Ionian Sea is about 270 million years old. (The oldest parts of continental crust, on the other hand, are more than 4 billion years old.) Geologists collect samples of oceanic crust through drilling at the ocean floor, using submersible s, and studying ophiolites. Ophiolite s are sections of oceanic crust that have been forced above sea level through tectonic activity, sometimes emerging as dike s in continental crust. Ophiolites are often more accessible to scientists than oceanic crust at the bottom of the ocean. Continental Crust Continental crust is mostly composed of different types of granites. Geologists often refer to the rocks of the continental crust as “sial.” Sial stands for silicate and aluminum, the most abundant minerals in continental crust. Sial can be much thicker than sima (as thick as 70 kilometers kilometers (44 miles)), but also slightly less dense (about 2.7 grams per cubic centimeter (1.6 ounces per cubic inch)). As with oceanic crust, continental crust is created by plate tectonics.

At convergent plate boundaries, where tectonic plates crash into each other, continental crust is thrust up in the process of orogeny , or mountain-building. For this reason, the thickest parts of continental crust are at the world’s tallest mountain ranges. Like iceberg s, the tall peaks of the Himalayas and the Andes are only part of the region’s continental crust—the crust extends unevenly below the Earth as well as soaring into the atmosphere. Craton s are the oldest and most stable part of the continental lithosphere. These parts of the continental crust are usually found deep in the interior of most continents. Cratons are divided into two categories. Shield s are cratons in which the ancient basement rock crops out into the atmosphere. Platform s are cratons in which the basement rock is buried beneath overlying sediment . Both shields and platforms provide crucial information to geologists about Earth’s early history and formation. Continental crust is almost always much older than oceanic crust. Because continental crust is rarely destroyed and recycled in the process of subduction, some sections of continental crust are nearly as old as the Earth itself.

Extraterrestrial Crust Our solar system’s other terrestrial planets (Mercury, Venus, and Mars) and even our own Moon have crusts. Like Earth, these extraterrestrial crusts are formed mostly by silicate minerals. Unlike Earth, however, the crusts of these celestial bodies are not shaped by the interaction tectonic plates. Despite the Moon’s smaller size, lunar crust is thicker than crust on Earth. Lunar crust is not a uniform thickness and in general tends to be thicker on the “far side,” which always faces away from Earth. Although Mercury, Venus, and Mars are not thought to have tectonic plates, they do have dynamic geology. Venus, for instance, has at partly- molten mantle, but the Venusian crust lacks enough trapped water to make it as dynamic as Earth’s crust. The crust of Mars, meanwhile, features the tallest mountains in the solar system. These mountains are actually extinct volcano es formed as molten rock erupt ed in the same spot on the Martian surface over millions of years. Eruptions built up enormous mountains of iron-rich igneous rocks that give the Martian crust its characteristic red hue . One of the most volcanic crusts in the solar system is that of Jupiter’s moon Io.

The rich sulfide rocks in the Ionian crust paint the moon a dappled collection of yellows, greens, reds, blacks, and whites. Term relatively easy to approach, use, or obtain. accumulation having to do with the surrounding area or environment. arid type of dark volcanic rock. basement rock oldest underlying rock formation in any region. boundary physical, cultural, or psychological feature of an organism, place, or object. Conrad discontinuity seismic boundary between the continental crust and oceanic crust. continental crust thick layer of Earth that sits beneath continents. convergent plate boundary Noun area where two or more tectonic plates bump into each other. Also called a collision zone. core old, stable part of continental crust, made up of shields and platforms. crucial spotted, or having areas of differently colored shades or tones. dense having parts or molecules that are packed closely together. desert Noun capable of withstanding a certain amount of force by changing form before fracturing or breaking. dynamic always changing or in motion. Earth Noun our planet, the third from the Sun. The Earth is the only place in the known universe that supports life. to explode or suddenly eject material.

eventually at some point in the future. extinct volcano volcano that will no longer erupt. extraterrestrial located or formed outside Earth's atmosphere. geologic having to do with the physical formations of the Earth. granite type of hard, igneous rock. granite type of hard, igneous rock. hue tint or general variety of color. iceberg rock formed by the cooling of magma or lava. incompatible element Noun in geochemistry, an element that stays in a liquid phase during the melt or crystallization process. initially chemical element with the symbol Fe. isostasy Noun equilibrium of Earth's crust, where the forces tending to elevate landmasses balance those tending to depress them. Also called isostatic equilibrium. lava molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface. lithosphere having to do with Earth's moon or the moons of other planets. magma chemical element with the symbol Mg. malleable flexible and capable of reforming itself without breaking when under stress. mantle mantle convection Noun slow movement of Earth's solid mantle caused by convection currents transferring heat from the interior of the Earth to the surface.

metal category of elements that are usually solid and shiny at room temperature. metamorphic rock rock that has transformed its chemical qualities from igneous or sedimentary. mid-ocean ridge inorganic material that has a characteristic chemical composition and specific crystal structure. Mohorovicic discontinuity point between Earth's crust and the mantle below. Also called the Moho. molten solid material turned to liquid by heat. ocean basin depression in the Earth's surface located entirely beneath the ocean. oceanic crust thin layer of the Earth that sits beneath ocean basins. ocean trench remnant of oceanic crust (certain igneous rocks) embedded in continental crust. orogeny the way mountains are formed. outgas to release a gas that was dissolved, trapped, frozen or absorbed in another material. planet platform Noun ancient rocks that formed as part of continental crust, now overlain with sediment and sedimentary rock, located in the interior of continents. rock natural substance composed of solid mineral matter. sediment rock formed from fragments of other rocks or the remains of plants or animals. shield Noun ancient rocks that formed as part of continental crust and are located in the interior of continents.

sial rocks, mostly silicates and aluminum, making up most of Earth's continental crust. silica chemical compound (SiO2) that makes up most of the Earth's rocks. silicate Noun most common group of minerals, all of which include the elements silicon (Si) and oxygen (O). sima rocks, mostly silicates and magnesium, making up most of Earth's oceanic crust. subduction process of one tectonic plate melting, sliding, or falling beneath another. subduction zone area where one tectonic plate slides under another. submersible small submarine used for research and exploration. sulfide (S2-) negatively charged ion of sulfur, or a chemical compound containing such an ion. tectonic activity movement of tectonic plates resulting in geologic activity such as volcanic eruptions and earthquakes. tectonic plate Noun massive slab of solid rock made up of Earth's lithosphere (crust and upper mantle). Also called lithospheric plate. temperature one of the four planets closest to the sun: Mercury, Venus, Earth, or Mars. transition zone Noun areas in the Earth's interior between the upper mantle, near the Earth's crust, and the lower mantle, near the Earth's core.

uniform exactly the same in some way. universe all known matter, energy, and space. viscous liquid that is thick and sticky. volcano Noun an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions. The Earth's Crust: Everything You Need to Know By Andrew Alden Updated May 07, 2016. The Earth's crust is an extremely thin layer of rock that makes up the outermost solid shell of our planet. In relative terms, it's thickness is like that of the skin of an apple. It amounts to less than half of 1 percent of the planet's total mass but plays a vital role in most of Earth's natural cycles. The crust can be thicker than 80 kilometers in some spots and less than one kilometer thick in others. Underneath it is lies the mantle , a layer of silicate rock approximately 2700 kilometers thick. The mantle accounts for the bulk of the Earth. The crust is composed of many different types of rocks that fall within three main categories: igneous , metamorphic and sedimentary . However, most of those rocks originated as either granite or basalt.

The mantle beneath is made of peridotite. Bridgmanite, the most common mineral on Earth , is found in the deep mantle. How We Know the Earth Has a Crust We didn't know the Earth had a crust until the early 1900s. continue reading below our video Test Your General Science Knowledge Up until then, all we knew was that our planet wobbles in relation to the sky as if it had a large, dense core - astronomical observations told us so. Then along came seismology, which brought us a new type of evidence from below: seismic velocity. Seismic velocity measures the speed at which earthquake waves propagate through the different materials (i.e. rocks) below the surface. With a few important exceptions, seismic velocity within the Earth tends to increase with depth. In 1909, a paper by the seismologist Andrija Mohorovicic established a sudden change in seismic velocity - a discontinuity of some sort - about 50 kilometers deep in the Earth. Seismic waves bounce off it (reflect) and bend (refract) as they go through it, the same way that light behaves at the discontinuity between water and air.

That discontinuity, named the Mohorovicic discontinuity or "Moho," is the accepted boundary between the crust and mantle. Crusts and Plates The crust and tectonic plates are not the same thing. Plates are thicker than the crust and consist of the crust plus the shallow mantle just beneath it. This stiff and brittle two-layered combination is called the lithosphere ("stony layer" in scientific Latin). The lithospheric plates lie on a layer of softer, more plastic mantle rock called the asthenosphere ("weak layer"). The asthenosphere allows the plates to move slowly over it like a raft in thick mud. We know that the Earth's outer layer is made of two grand categories of rocks: basaltic and granitic. Basaltic rocks underlie the seafloors and granitic rocks make up the continents. We know that the seismic velocities of these rock types, as measured in the lab, match those seen in the crust down as far as the Moho. Therefore we're confident that the Moho marks a real change in rock chemistry. The Moho isn't a perfect boundary, because some crustal rocks and mantle rocks can masquerade as the other.

However, everyone who talks about the crust, whether in seismological or petrological terms, fortunately means the same thing. In general, then, there are two kinds of crust: oceanic crust (basaltic) and continental crust (granitic). Oceanic Crust Oceanic crust covers about 60 percent of the Earth's surface. Oceanic crust is thin and young—no more than about 20 km thick and no older than about 180 million years . Everything older has been pulled underneath the continents by subduction . Oceanic crust is born at the mid-ocean ridges, where plates are pulled apart. As that happens, the pressure upon the underlying mantle is released and the peridotite there responds by starting to melt. The fraction that melts becomes basaltic lava, which rises and erupts while the remaining peridotite becomes depleted. The mid-ocean ridges migrate over the Earth like Roombas , extracting this basaltic component from the peridotite of the mantle as they go. This works like a chemical refining process. Basaltic rocks contain more silicon and aluminum than the peridotite left behind, which has more iron and magnesium. Basaltic rocks are also less dense.

In terms of minerals, basalt has more feldspar and amphibole, less olivine and pyroxene, than peridotite. In geologist's shorthand, oceanic crust is mafic while oceanic mantle is ultramafic. Oceanic crust, being so thin, is a very small fraction of the Earth - about 0.1 percent - but its life cycle serves to separate the contents of the upper mantle into a heavy residue and a lighter set of basaltic rocks. It also extracts the so-called incompatible elements, which don't fit into mantle minerals and move into the liquid melt. These in turn move into the continental crust as plate tectonics proceeds. Meanwhile, the oceanic crust reacts with seawater and carries some of it down into the mantle. Continental Crust Continental crust is thick and old - on average about 50 km thick and about 2 billion years old - and it covers about 40 percent of the planet. Whereas almost all of the oceanic crust is underwater, most of the continental crust is exposed to the air. The continents slowly grow over geologic time as oceanic crust and seafloor sediments are pulled beneath them by subduction.

The descending basalts have the water and incompatible elements squeezed out of them, and this material rises to trigger more melting in the so-called subduction factory . The continental crust is made of granitic rocks, which have even more silicon and aluminum than the basaltic oceanic crust. They also have more oxygen thanks to the atmosphere. Granitic rocks are even less dense than basalt. In terms of minerals, granite has even more feldspar and less amphibole than basalt and almost no pyroxene or olivine. It also has abundant quartz . In geologist's shorthand, continental crust is felsic. Continental crust makes up less than 0.4 percent of the Earth, but it represents the product of a double refining process, first at mid-ocean ridges and second at subduction zones. The total amount of continental crust is slowly growing. The incompatible elements that end up in the continents are important because they include the major radioactive elements uranium , thorium and potassium. These create heat, which makes the continental crust act like an electric blanket on top of the mantle. The heat also softens thick places in the crust, like the Tibetan Plateau , and makes them spread sideways.

Continental crust is too buoyant to return to the mantle. That's why it is, on average, so old. When continents collide, the crust can thicken to almost 100 km, but that is temporary because it soon spreads out again. The relatively thin skin of limestones and other sedimentary rocks tend to stay on the continents, or in the ocean, rather than return to the mantle. Even the sand and clay that is washed off into the sea returns to the continents on the conveyor belt of the oceanic crust. Continents are truly permanent, self-sustaining features of the Earth's surface. What the Crust Means The crust is a thin but important zone where dry, hot rock from the deep Earth reacts with the water and oxygen of the surface, making new kinds of minerals and rocks. It's also where plate-tectonic activity mixes and scrambles these new rocks and injects them with chemically active fluids. Finally, the crust is the home of life, which exerts strong effects on rock chemistry and has its own systems of mineral recycling. All of the interesting and valuable variety in geology, from metal ores to thick beds of clay and stone, finds its home in the crust and nowhere else.

It should be noted that the Earth isn't the only planetary body with a crust. Venus, Mercury, Mars and the Earth's Moon have one as well . Inside the Earth [This Dynamic Earth, USGS] Inside the Earth The size of the Earth -- about 12,750 kilometers (km) in diameter-was known by the ancient Greeks, but it was not until the turn of the 20th century that scientists determined that our planet is made up of three main layers: crust, mantle, and core. This layered structure can be compared to that of a boiled egg. The crust, the outermost layer, is rigid and very thin compared with the other two. Beneath the oceans, the crust varies little in thickness, generally extending only to about 5 km. The thickness of the crust beneath continents is much more variable but averages about 30 km; under large mountain ranges, such as the Alps or the Sierra Nevada, however, the base of the crust can be as deep as 100 km. Like the shell of an egg, the Earth's crust is brittle and can break. Cutaway views showing the internal structure of the Earth.

Below: This view drawn to scale demonstrates that the Earth's crust literally is only skin deep. Below right: A view not drawn to scale to show the Earth's three main layers (crust, mantle, and core) in more detail (see text). Below the crust is the mantle, a dense, hot layer of semi-solid rock approximately 2,900 km thick. The mantle, which contains more iron, magnesium, and calcium than the crust, is hotter and denser because temperature and pressure inside the Earth increase with depth. As a comparison, the mantle might be thought of as the white of a boiled egg. At the center of the Earth lies the core, which is nearly twice as dense as the mantle because its composition is metallic (iron-nickel alloy) rather than stony. Unlike the yolk of an egg, however, the Earth's core is actually made up of two distinct parts: a 2,200 km-thick liquid outer core and a 1,250 km-thick solid inner core. As the Earth rotates, the liquid outer core spins, creating the Earth's magnetic field. Not surprisingly, the Earth's internal structure influences plate tectonics.

The upper part of the mantle is cooler and more rigid than the deep mantle; in many ways, it behaves like the overlying crust. Together they form a rigid layer of rock called the lithosphere (from lithos, Greek for stone). The lithosphere tends to be thinnest under the oceans and in volcanically active continental areas, such as the Western United States. Averaging at least 80 km in thickness over much of the Earth, the lithosphere has been broken up into the moving plates that contain the world's continents and oceans. Scientists believe that below the lithosphere is a relatively narrow, mobile zone in the mantle called the asthenosphere (from asthenes, Greek for weak). This zone is composed of hot, semi-solid material, which can soften and flow after being subjected to high temperature and pressure over geologic time. The rigid lithosphere is thought to "float" or move about on the slowly flowing asthenosphere. The Earth's Layers Lesson #1 The Earth's Layers Lesson #1 The Four Layers The Earth is composed of four different layers. Many geologists believe that as the Earth cooled the heavier, denser materials sank to the center and the lighter materials rose to the top.

Because of this, the crust is made of the lightest materials (rock- basalts and granites) and the core consists of heavy metals (nickel and iron). The crust is the layer that you live on, and it is the most widely studied and understood. The mantle is much hotter and has the ability to flow. The Outer and Inner Cores are hotter still with pressures so great that you would be squeezed into a ball smaller than a marble if you were able to go to the center of the Earth!!!!!! The Crust The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 3-5 miles (8 kilometers) thick under the oceans( continental crust ). The temperatures of the crust vary from air temperature on top to about 1600 degrees Fahrenheit (870 degrees Celcius) in the deepest parts of the crust. You can bake a loaf of bread in your oven at 350 degrees Fahrenheit , at 1600 degrees F. rocks begin to melt. The crust of the Earth is broken into many pieces called plates. The plates "float" on the soft, mantle which is located below the crust.

These plates usually move along smoothly but sometimes they stick and build up pressure. The pressure builds and the rock bends until it snaps. When this occurs an Earthquake is the result! Notice how thin the crust of the Earth is in comparison to the other layers. The seven continents and ocean plates basically float across the mantle which is composed of much hotter and denser material. The crust is composed of two basic rock types granite and basalt. The continental crust is composed mostly of granite. The oceanic crust consists of a volcanic rock called basalt. Basaltic rocks of the ocean plates are much denser and heavier than the granitic rock of the continental plates. Because of this the continents ride on the denser oceanic plates. The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the . The asthenosphere is the part of the mantle that flows and moves the plates of the Earth. The Mantle The mantle is the layer located directly under the sima. It is the largest layer of the Earth, 1800 miles thick. The mantle is composed of very hot, dense rock. This layer of rock even flows like asphalt under a heavy weight.

This flow is due to great temperature differences from the bottom to the top of the mantle. The movement of the mantle is the reason that the plates of the Earth move! The temperature of the mantle varies from 1600 degrees Fahrenheit at the top to about 4000 degrees Fahrenheit near the bottom! Convection Currents The mantle is made of much denser, thicker material, because of this the plates "float" on it like oil floats on water. Many geologists believe that the mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling, sinking again and then heating, rising and repeating the cycle over and over. The next time you heat anything like soup or pudding in a pan you can watch the convection currents move in the liquid. When the convection currents flow in the mantle they also move the crust. The crust gets a free ride with these currents. A conveyor belt in a factory moves boxes like the convection currents in the mantle moves the plates of the Earth. Outer Core The core of the Earth is like a ball of very hot metals. (4000 degrees F.

to 9000 degrees F.) The outer core is so hot that the metals in it are all in the liquid state. The outer core is located about 1800 milesbeneath the crust and is about 1400 miles thick. The outer core is composed of the melted metals nickel and iron. Inner Core The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place as a solid. The inner core begins about 4000 miles beneath the crust and is about 800 miles thick. The temperatures may reach 9000 dgrees F. and the pressures are 45,000,000 pounds per square inch. This is 3,000,000 times the air pressure on you at sea level!!! Answer the following questions on a sheet of paper with your partner. If you need to look back to find the answers use the page titles located directly under the questions to help you. When you finish the questions click on the Earth icon to return the program to the beginning. 1.

Name the four layers of the Earth in order from the outside to the center of the Earth. 2. What causes the mantle to "flow"? 3. What are the two main metals that make up the outer and inner core? 4. Describe in your own words how the Earth's layers were formed. "The Four Layers" will help you. The Layers of the Earth - Planet Earth Planet Earth HELP! Layers of the Earth Uh oh! I don't know anything about the "Layers of the Earth" and nothing about how many layers there are but luckily my website has as section of Earth Layers. Here are the most main information you should know about the "layers", there are 4 layers in the earth, the crust, the massive mantle, outer core and the solid inner core. The Crust is the thinnest layer in the earth. The Mantle is very massive (huge) if you don't get huge imagine it takes up 80% of the earth now that is huge. The outer core is made of iron and nickel. The inner core is the most inner layer it is very solid. I bet you need more information if you do just scroll down and you'll find non-confusing information.

Crust The crust is the most outer layer of the Earth. The crust is very rigid (Hard). The crust is made of granite and basalt. The ocean basically takes up 70% of the crust. The thin rocky crust is made out of silicon, aluminum, calcium, sodium and potassium . The crust is divided into continental plates that drift slowly every year (about a few centimeters). Just a few kilometers below your feet, its molten rock, extending to for thousands of kilometers down to the planet's super heated iron core. The entire earth's crust occupies just 1% of the earth's volume. The Earth's crust thickness is 30 km thick. The temperature of the crust is 2oo degrees Celsius (392 Fahrenheit) to 400 degrees Celsius (752 Fahrenheit). Mantle The Mantle is the second layer of the earth, it takes up 80% of the Earth. The mantle has two sections (Lithosphere and the Asthenosphere). The temperature of the lithosphere and asthenosphere is 300 to 500 degrees celsius. The mantles temperature 4500 degrees celsius and made of 100% magma.

In the mantle, convection currents occur. The convection currents occurs in the lithosphere and the asthenosphere. The mantle is very deep it is 1800- 2900 kilometers deep. A very interesting fact is that the mantle grows about a meter every year. Lithosphere The lithosphere is the upper part of the mantle. The Lithospheres temperature is about 400 degrees celsius. The lithosphere (lower mantle) is rigid part of the mantle. The lithosphere is not only part of the mantle it is the crust and the upper part of the mantle together. The depth of the lithosphere is 50-100 km thick. Asthenosphere The asthenosphere is the lower part of the mantle. The asthenosphere temperature is 300-500 degrees Celsius. The asthenosphere is ductile and can be pushed and deformed like silly putty in response to the warmth of the Earth. These rocks actually flow, moving in response to the stresses placed upon them by the motions of the deep interior of the Earth. The flowing asthenosphere carries the lithosphere of the Earth, including the continents, on its back.

Convection Currents In the mantle are "convection currents" ,which make the mantle move. The lower mantle heats up and rises and cools down then gets pushed down because it is heavier. The currents keeps on going round and round. Convection currents occur because of density of a fluid is related to its temperature. Hot rocks lower in the mantle are less dense than their cooler counterparts below. The hot rock rises and the cooler rock sinks due to gravity. Outer Core The outer core is the third layer of the earth. The outer core surrounds the inner core . The outer core is the only liquid layer of the Earth. You could say that the outer core is basically a sea of iron and nickel. The outer core is 2100 miles and also is in an range of 200-300 kilometres thick. 7,200 to 9,000 degrees Fahrenheit (4,000 to 5,000 degrees Celsius). Inner Core The inner core is the most inner layer of the earth. The inner core contains iron, the iron in the inner core is not pure (so not just iron) scientists believe it contains sulfur and nickel and also smaller amount of other elements.

The inner core is extremely hot it is somewhere between 9000 and 13000 degrees Fahrenheit (5000 and 7000 degrees Celsius). Create a free website

Question: In geology what is the layer below the earth’s crust?
Answer: The Mantle